<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // 一,顶级作用域非方法调用?
    // 顶级的非方式调用会将this指为window,(在严格模式下,this为undefined而不是window)
  </script>
</body>
</html>